It is enough to visit these places in 1.5 day. You could spend one day to go to the great wall; on the way, it is worthy to visit the Ming Tombs(https://www.travelchinaguide.com/attraction/beijing/ming_tomb.htm) . At night, you may also try some local snacks in Snack Streets, Beijing(https://www.travelchinaguide.com/cityguides/beijing/dinning/snackstreet.htm) .The next 0.5 day, go to the Forbidden City and the Tiananmen Square for a short view. Here are some suggeated Beijing Tour Packages(https://www.travelchinaguide.com/package/beijing.htm) for your reference~